Other related questions:

Possible causes are:
-DHCP is not enabled globally using the dhcp enable command in the system view.
-The address pool is not configured using the dhcp select interface or dhcp select global command in the interface view.
-The dhcp select global command in executed in the interface view, but the global address pool is incorrectly configured.
-Wireless users use MAC address authentication, but no MAC address is configured for the users on the authentication server.

The causes that DHCP clients fail to obtain IP addresses from the DHCP server are as follows:
- The configuration is incorrect.
- There is no allocable IP address in the DHCP address pool.
- STP is enabled on upper-level access devices of some diskless workstations. For details on troubleshooting and solutions, see AR150&AR160&AR200&AR510&AR1200&AR2200&AR3200 FAQ.

About the AR ClientExceptions occurs when the IP address is obtained. For details, see the Revelations of Troublesolving on the right page.

For S series switches (except the S1700):
For example, in a network composed of the AC, S5700, and AP, the AC assigns an IP address to the AP using DHCP. If the AP does not obtain any IP address, troubleshoot this fault on the switch as follows:
- Run the display arp command to check whether the switch has learned the MAC addresses of the connected AC and AP.
- Run the display dhcp snooping configuration command to check whether DHCP snooping is configured on the switch. If so, DHCP packets received on the interfaces between the switch and the AC or AP are filtered.
If no error is found, check the configurations on the AC and AP.